This invention relates to providing an article for absorbing body fluids. More particularly, this invention relates to an absorbent pad for use in such products as sanitary napkins, panty liners, diapers and the like.
In general, such products comprise one or more layers of a core of hydrophilic material such as wood pulp, rayon tissue or the like. The hydrophilic material, generally fibrous in form, is provided as a pad having a rectangular or oblong shape or in some cases, a shape designed to fit the anatomy of the wearer more closely. Such products may also be designed to have wings or flaps, which extend transversely from the product and serve to protect the wearer's panty from becoming stained due to the tendency for body fluid to flow over the sides of the napkin. The pad is usually provided with an enveloping cover pervious to body fluids on the side of the pad which is to be placed against the body and impervious to such fluids on the side facing away from the body. The object of such a body fluid impervious cover is, of course, to protect the clothing from staining and wetting.
In general, such products have satisfactorily performed their function of absorbing and retaining body fluids and preventing staining and wetting of the wearer's clothing. When the product is properly placed and retained by the wearer in its intended position, body fluid is directed at or near the center of the product and is distributed, by means of liquid wicking, throughout the absorbent medium. However, in a significant number of cases, the product is misplaced, either by the wearer when she initially places the product, or by her activities. Under these circumstances, body fluid will strike the pad off-center and closer to the peripheral edges of the pad. This off-center deposition of body fluid is believed to be the cause of a significant number of failures associated with the use of these products, i.e., the staining and wetting the clothing of the wearer by body fluid. Such failures are known as "side failures".
Even when the product has not been misplaced by the wearer, there are a significant number of failures at the sides of the product. Flow through the absorbent medium after deposition of body fluid is both lateral and longitudinal. Because the distance between the sides of the product is relatively small, fluid can travel laterally and cause side failure quickly.
In the past, there have been efforts to direct the flow of body fluid using baffles or densified sheets. For example, U.S. Pat. No. 3,375,827 (Bletzinger et al.) describes a flow control element located on the body facing side of a main absorbent element of a sanitary napkin. Bletzinger et al. describe the flow control element as a compressed strip of absorbent material of smaller dimension in length and width than the main absorbent element. However, the flow control element rests directly on top of the absorbent core. Thus, the fluid flows radially around and through the flow control element to the core. The fluid, therefore, can flow transversely to the sides of the pad as well as longitudinally, causing side failure.
U.S. Pat. No. 3,612,054 (Matsuda) describes a sanitary napkin having three layers of absorbent material and barrier sheets of liquid repellent material interposed between the layers. Although the barrier sheets are intended to utilize the full capacity of the absorbent layers, they do not address the problem of side failure. Fluid is able to leak throughout the absorbent layers and out the sides of the napkin.
U.S. Pat. No. 4,282,874 (Mesek) describes a diaper having a densified layer. The densified layer is intended to provide a "wickability" gradient which rapidly transmits fluid away from the body-facing layer without permitting it to flow back toward the body. Mesek does not, however, address the problem of preventing leakage at the sides of an absorbent article.
Thus, it is an object of this invention to provide an absorbent article which substantially prevents the flow of body fluid to the sides of the article so as to limit or prevent side failure.
It is another object of this invention to provide an absorbent article such as a sanitary napkin which is capable of directing flow of body fluid along the longitudinal axis of the article.
Yet another object of this invention is to provide an absorbent product in which a large proportion of the absorbent capacity is utilized.